Wireless telephone system



F. CONRAD WIRELESS TELEPHONE SYSTEM Filed March 15, 1922 Mar. 3. 1925.

WITNESSES:

INVENTOR Frank Con/ad I BY :7 AT'TORNEY Patented Mar. 3,,1925.

UNITED STATES FRANK CONRAD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0WESTINGHOUSE P QYTEVNT' OFFICE.

ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

WIRELESS TELEPHONE SYSTEM.

Application filed March- 15, 1922. Serial No. 544,005.

To all whom it may concern:

Be it'known' that I, FRANK CONRAD, a citizen, of the United States, anda resident of Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in, W1relesswirele s telephone systems, whereby the transmission of speech by meansof radiant energy may be more readily effected. p

' More specifically, one object of my invention is to provide amodulatin system which shall be particularly adapte to highpowerwireless telephone systems. Another object of my invention is to providea modulating system which employs a thermionictube as a modulator andwhich is so associated with energy-absorbing circuits that onlyrelatively small amounts of energy are dissipated in the modulator tubeitself, the larger oi'tion thereof being dissipated in the a sorbingcircuit.

A further object of my invention is to provide a wireless telephonesystem employing distinct radiating and absorbing circults, one of whichis tuned to a natural frequency slightly above the frequency of thehigh-frequency supply-currents, the other circuit-bein tuned toa'natural frequency slightly be ow the suppl frequency, together withmeans for mo ulating the frequency of the supply-currents, whereby aconstant load is maintained.

Other objects of, my invention will be apparent from the followingdescription and claims, when considered in connection with theaccompanying drawing, wherein:

nFigure 1 is; a diagrammatic view of a wireless telephone systemembodying my invention;

Fig. 2 is a similar view showing'analternative arrangement of thecircuits, and Fig. 3 1s a curve diagram showing 'the variation of thecurrent in the antenna and absorbingv circuits in accordance with thefrequency of the supply-current. a In Fig. 1 is shown apair'ofthermionic 'ment electrodes 5, 6, 7 and 8.

' valves 1 and 2 comprising, respectively,

input electrodes 3, 4s and output plate-fila- The' filament electrodes 7and 8 of the tubes 1 and 2, respectively, may be energized from e1 ergysources 9 and'll through resistors 12' and 13 and are-connected in.parallel relation' by means of a conductor 14. The inputelectrodes orgrids 3, 4 are connected in parallel by means of a conductor 15. Theremaining output electrodes or plates 5, 6 are connected in parallel bymeans of a conductor 16 which includes a pair of ra-' dio-frequencychoke coils 17 and 18.

One terminal of source 20 of-direct-current energy is connected, bymeans of a conductor 19, through achoke coil 21, to a oint'ontheconductor 16, intermediate the choke coils 17 and 18. The remainingterminal of the source 20 of direct-current energy is connected, bymeans of a conductor 22, to the conductor 14. The choke coil 21 is sodesigned as to maintain a substantially constant power-supply to thethermionic tubes 1 and 2 under all conditions of operation. I

For purposes of illustration, an oscillation generator system 24 is.shown as an os-' cillator-tube system of known form, comprising athermionic tube 25 having an anode 26, a control electrode 27 and a hotcathode 28 disposed therein. The hot cathode 28 may be energized bymeans of an energy source 29 through a resistor 31.

A plate-filamentv circuit comprises a por- .of the currents generated bythe oscillation generator system 24in accordance with variations 1nntensity of sound waves. An

rect-current .source 36 in series with .a choke coil 23.

A conductor "38 extends from the anodev 26 of the osei-lla-tortube 25 tothe conductor .tion 3234 of a tuning coil 33 and a stop 'anodewathodccurrent is supplied by a di- V v 15 which connects the grids of thevacuum tubes 1 and 2' in parallel. The cathode 28 of the oscillator tube25 is connected to the ment circuit of the oscillation generator system24 is directly connected across the grids 3, 4 and the filaments 7, 8 ofthe vacuum tubes 1 and-2, respectively, the potentials of the grids arevaried at frequencies corresponding to' those of the oscillationgenerator system 24.

The anode 5 of the thermionic tube 1 is connected, by a conductor 41, toa tuning coil 38 through a stopping condenser 42. The cathode 7 of thethermionic tube is connected to the coil 38' by a conductor 39. Anantenna circuit 43 is operative'ly associated with the tuning coil 38'.

The modulator tube 2 is provided with a plate-filament circuit includinga parallelresonant circuit 45 which may include a tuning coil 46, anenergy-absorbing element 47 and a stopping condenser 48, shunted by avariable tuning condenser 49. The condenser 48 is "so designed as tohaverelatively low-impedance to currents of radio-frequency. The periodof the parallel-resonant circuit may be adjusted to any desired value bythe variable condenser 49.

The modification of my invention shown in Fig. 2 differs from that ofFig. 1 in that the lead 38a is connected only to the grid 4 of the tube2,,and the tube 1 isconnected'to function as an oscillator tube in anoscillation generator system 51 similar to that employed with the tube25. An additional modification consists in the employment of aninductive coupling between the oscillation generator system 51 and theantenna circuit 43. To secure best results, the coupling just mentionedshould be tight.

In the operation of the system shownin Fig. 1,-the naturalfrequencies ofthe antenna circuit 43 and of the absorption circuit 45 are adjusted tothe resonant frequencies F1 anl F2, as indicated in the curve diagram 55and 56, respectively, shown'in Fig. 3, where ordinates representintensities of currents and abscissaa represent the correspondingfrequencies.

The frequency of the oscillation generator system 24 is then adjusted toa value F intermediate the frequencies F and F When sound waves enterthecondenser transmitter 37, the frequency of the currents generated bythe oscillation generator system 24. is correspondingly varied. Themodulated energy of the oscillation generator system 24 is thenimpressed upon the grids of the amplifier tube 1 'and'of the modulatortube 2 to cause the passage of highfrequency currents havingsimilarcharacteristics in the antenna circuit and in the absorption circuit.

As can readilybe seen by referring to the resonance curves shown in Fig.3, the effect.

of an increasein the frequency of the curing circuit'43 and to increasethat taken by the absorbing circuit 45, and vice versa-. Thus, theenergy in the antenna circuit is modulated in amplitude in accordancewith the variations in frequency effected by the condenser transmitter37, while the total current flowing in the direct-current source 20 issubstantially constant, owing to the fact that the curves 55 and 56, atthe frequency F, have slopes that are equal numerically but opposite insign. The controlling power supplied by the oscillator tube 25 is alsoconstant, since its frequency only is varied.

The constants of the resonant circuit 45 are so adjusted that acondition is secured wherein the energy dissipated in the tube 2 isextremely small, as compared With the energy dissipated in the resonantcircuit 45 in the plate-filament circuit of the tube,

thereby admitting of the use of tubes of Fig. 2 is somewhat dilfereiitfrom that of Fig. 1 in that the amplifier'tube 1 is caused to serve. asan oscillator tube. Modulation of the high-frequency energy is effectedthrough the control of the power-supply to the oscillator tube, in amanner hereinafter described.

In this arrangement, the efl'ect of speaking into the telephonetransmitter 37 is to cause the frequency of the currents in theplate-filament circuit45 to approach ,and recede from theresonant-frequency of that circuit, thereby varying the power absorbed.

The power delivered to the tubes 1 and 2 remains constant in value byreason of the choke-coil 21, under all workingconditions. The effect ofvarying the power absorbed by the absorption circuit is, therefore, tocorrespondingly vary the power delivered to the tube 1. Since variationsin the power supplied to tube 1 effect similar changes in the energysupplied, to the antenna circuit,- the resulting modulation of theradiant energy issimilar'tmthat obtained in the previous system.

While I have shown but twoembodiments of m invention, I do not wish tobe limited there y, and I desire that only such limitations shall beimposed upon my invention as are indicated .in the appended claims.

I claim as my invention:

1. In an electrical system, a pair jot parallelassociated evacuatedelectric devices having space-current'paths therein, input and outputelectrodes individual to each space-current path, means associated withsaid input electrodes for impressing elec device, said circuits being sotuned that said modulations in frequency cause opposite variations inthe relative amounts of power absorbed by the respective circuits.

2. In an electrical system, a pair of parallel-associated evacuatedelectric devices having space-current paths therein, input and output.electrodes individual to each space-current path, means associated withsaid input electrodes for impressing highfrequency electrical energythereon, means for modulating the frequency of said energy according tothe signals to be transmitted, and an energy-absorbing circuitassociated with the output electrodes of each device, said circuitsbeing so tuned that said modulations in frequency cause oppositevariations .in the relative amounts of power ab- 'sorbed by therespective circuits.

In a wireless system, a pair of parallel-associated evacuated electricdevices having space-cuprent paths therein, input and output eletztrodesindividual to each space-current path, means for energizing saiddevices, a circuit carrying frequencymodulated, high-frequencysignal-currents associated with said input electrodes, and two circuits,one for translating energy and the other forabsorbing energy, associatedwith the output'electrodes of the respective device's, said circuitsbeing tuned to different frequencies, one above and the other below thefrequencies of said signal-currents.

4. In a wireless system, a pair ofpa'rallelassociated relays, each ofsaid relays having a supply circu1t,-a control circuit and a loadcircuit, common means associated'with both of said control circuits forimpressing high frequency electrical energy thereon modulated infrequency in accordance-with signals to be reproduced, anenergy-absorbing device associated with the load circuit" of eachdevice, and tuning means associated with said devices andsaid loadcircuits, said tuning means being so tuned that increases in thefrequency of theimpressed energy upon said control circuits increasesthe power absorbed in one device and decreases that absorbed. in theother device.

5. In an electrical system, a supply circuit, a pair of parallel pathsconnected therein, an evacuated electric device having aspace-currentpath therein connected in each of said parallel paths, input and outputelectrodes for each space-current path, similar electrodes beingoperatively connected, energy-absorbing circuits associated with each ofsaid evacuated electric devices constant-power currents of modulatedfrequency, said absorbing circuits being so tuned that the modulationsin I frequency cause opposite variations'in the power absorbed by therespective circuits.

6. In a wireless system, a pair of parallelassociated evacuated electricdevices having space-current paths therein,- input and output electrodesfor each space-current path, means for energizing said devices, meansassociated with said input electrodes for impressing electrical energythereon modulated in frequency, an energy-absorbing circuit associatedwith the output electrodes of one of said devices and a usefulenergy-translating circuit operatively associated with the outputelectrodes of the remaining device, each of said circuits includingcapacitance and inductance, whereby the relative periods of saidcircuits may be so adjusted that said modulations in frequency causeopposite variations in the power absorbed by the respective circuits.

7. In a wireless system, a pair of parallel-.

connected relays, input and output terminals therefor, means forenergizing said relays, a tuned circuit including an energy-absorbingelement associated with the output terminals of one relay, a tunedradiating circuit operatively associated with the output terminals ofthe remaining relay and means for impressing high-frequency electricalenergy of varying frequency upon said input terminals, said circuitsbeing so tuned that said variations in frequency cause oppositevariations in the power absorbed by each circuit.

8. In a wireless transmission system, a pair of relays, each of saidrelays having a supply circuit, a control circuit and a load circuit, asubstantially constantpower source common to both of said supplycircuits, a tuned reactance means including an energy-absorbing elementassociated with the load circuit of one of said relays, a tunedreactance means ineludin a useful energy-translating device operative-1yassociated with the load circuit of the remaining relay, and means forimpressing high-frequency electrical energy of varying frequency upon atleast one of said control circuits, said reactance means being so tunedthat said modulations in frequency cause opposite variations in thepower absorbed by the energy-absorbing and translating devices.

'9. The method of varying the amplitude of currents in an antennacircuit which consists in generating radio-frequency currents, modifyingthe frequency of said currents in accordance with, a signal to betransmitted, impressing said currents upon the input circuits of a pairof parallel-com nected valves, each of which is associated with aradiating circuit and with an absorbing circuit and energized by asourceof energy, and so adjusting the tuning of said circuits that saidmodifications in the frequency of the impressed radio-frequency-currents cause opposite variations in the power absorbed by therespective circuits.

10. The method of signaling which consists in modulating the frequencyof the oscillations generated by a driver tube in accordance with soundwaves, impressing said oscillatory currents upon the grids of twoparallel-"connected tubes which are associated with a tuned radiatingcircuit and a tuned absorbing circuit, respectively, and so adjustingthe tuning of said circuits that said modulation in frequency'causesopposite variations in the power absorbed by the respective circuits.

11. The'method of modulation which consists in causing the powersupplied to an ing means for varying the frequency of said supplycircuit over a range intermediate the frequencies of said radiating andabsorbing circuits.

13. In an intelligen'ce-transmission system, the combination with twocoupled energy-translating circuits tuned to differ ent frequencies, ofa circuit coupled thereto carrying relatively high-frequency carriercurrents of intermediate frequency, said carrier-current frequency beingvaried within the limits of said translating-circuit frequency, inaccordance with a signal.

14. The combination with a source of alternating current, of atranslating device supplied thereby, and modulating means associatedtherewith forvarying the energy delivered to -said translating device,said modulating means comprising a parallel resonant circuit includingan energy-consuming element and tuned to a frequency slightly differentfrom that of the currents circulating therein, and means for pausingsaid frequency-difference to vary in accordslightly different than thatof said alternating currents, and means forcausing saidfrequency-difi'erence to vary in accordance with a signal. v 4

16. In an electrical system, a modulating device including aspace-current path, means disposed in operative relation to saidspace-current path for controlling the current therein, analternating-current circuit associated with said controlling means,whereby alternating-component. currents of corresponding frequency arecaused to circulate in said space-current path, an external circuit forsaid alternating-component currents comprising a parallelresonant pathtuned to a slightly different frequency, energy-absorbing meansassociated with said parallel-resonant path, and means for causing saiddifferences in frequency to vary.

In testimony whereof, I have hereunto subscribed my name this 4th day ofMarch, 1922.

' FRANK CONRAD.

